Japanese Patent Application Publication No. H05-270368 discloses a speed control system for controlling the speed of a vehicle to automatically keep the speed limit.
The speed control system includes a plurality of transceivers, a receiver, a speed detector, a comparator, and a brake controller. The plurality of transceivers are located on traffic lanes for vehicles. Each of the transceivers transmits a signal associated with the speed limit for vehicles. The receiver is installed in a vehicle to be controlled, and receives the signal transmitted from a transceiver to generate a first signal associated with the speed limit. The speed detector generates a second signal associated with the speed of the controlled vehicle that is running. The comparator compares the first signal with the second signal, and the brake controller receives the result of the comparison, and gives a third signal to the brakes of the controlled vehicle. Specifically, if the speed of the running controlled vehicle is higher than the speed limit, the brake controller actuates the brakes to reduce the speed of the controlled vehicle to be equal to or lower than the speed limit.